Positrons are the anti-particle of an electron, each having the same mass as an electron, but opposite charge. When a positron and electron combine, they annihilate, converting 100% of their mass into energy. Positrons are currently used in a wide range of applications including medicine, fundamental physics research, and materials characterization. High intensity positron sources may be critical in the creation of the world's first gamma-ray laser. Antimatter has the highest energy density of any known substance, and positrons have been studied by NASA as a possible propellant for high performance in-space propulsion systems.
Currently, the most intense source of positrons in the world produces 109 cold positrons per second. At this production rate, it would take over 10 million years to accumulate a milligram of positrons. In order to realize these newer concepts, a much more intense source of positrons must be developed.